A free app for Android, by L-Lingo.

We believe that learning Chinese Mandarin should be easy and fun. Therefore, we have developed the VocLab application with the purpose of making learning Chinese Mandarin as simple and effective as possible. Our application consists of a series of flashcards that are to be reviewed repeatedly by the user. This will help the user to remember the words and spell them correctly. At the same time, it is to be remembered that the words should be reviewed in the context of the sentences, to which they belong. 

Our flashcards consist of the most important Chinese Mandarin words, ranging from the basic words to the more advanced ones.